Flexible foraging strategies of gentoo penguins Pygoscelis papua over 5 years in the South Shetland Islands, Antarctica

Abstract

Gentoo penguins Pygoscelis papua show considerable plasticity in their diet, diving, and foraging behaviors among colonies; we expected that they might exhibit similar variability over time, at a single site, since flexible foraging habits would provide a buffer against changes in prey availability. We examined interannual changes in the foraging strategies and diet of gentoo penguins in the South Shetland Islands, Antarctica, over 5 years with variable prey abundance. Antarctic krill Euphausia superba was the primary diet item, and fish the secondary, though the importance of these items varied among years. Diving behavior also varied over time: different dive depth distributions were observed among years. Nonetheless, chick-rearing success remained relatively constant, indicating that gentoo penguins were able to maintain chick provisioning by altering their foraging strategy among years. Variable abundance of krill in the region did not have observable impacts on the diet, foraging behaviors or chick-rearing success of gentoo penguins. We suggest that foraging plasticity may be one reason that gentoo penguin populations have remained stable in the region, while their congeners (P. antarctica and P. adeliae) with less flexible foraging strategies have declined.

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Acknowledgments

Many thanks to all those who helped collect data associated with this study: I. Saxer, D. Schoeffler, L. Shill, M. Kappes, E. Leung, R. Orben, S. Chisholm and K. Pietrzak. Thanks also to A. Briggs who assisted with otolith identification and to D. Young and M. Polito who helped run statistical analyses. The US AMLR program and the National Science Foundation’s US Antarctic Program provided logistical support for the fieldwork. J. Hinke and 3 anonymous reviewers provided comments which greatly helped improve this manuscript. This research was funded by the US AMLR program and by the Lenfest Ocean Program of the Pew Charitable Trusts. All studies were conducted according to US law, and under approved animal use protocols of the University of California San Diego Institutional Animal Care and Use Committee.